Optical networks, such as OTN (Optical Transmission Network), WDM (Wavelength-Division Multiplexing), SDH (Synchronous Digital Hierarchy) or SONET (Synchronous Optical Network), have been widely applied in telecommunication field.
ASON (Automatic Switched Optical Network) is a research hotspot in optical network field in recent years. The definition of ASON provided by ITU-TG8080 protocol implements the function of ASON by setting a specific control plane (CP). The implementation framework of distributed call and connection in ASON is specified in ITU-TG.7713 to offer an implementing criterion for automatic establishment, modification and deletion of call and connection.
A series of standards such as ITU-TG8080 set forth the concept of domain. Generally, equipments from different manufacturers construct different ASONs, namely different domains. The domains interconnect with each other via exterior network interface (called E-NNI in ITU-T standards). The users connect with these domains via the user network interface (called UNI in ITU-T standards). From the logic viewpoint, each ASON device is equipped with control members having different functions, including connection controller responsible for the control of connection and call controller responsible for the implementation of call, wherein, the call controller includes the call controller of the device at the calling side or at the called side (called CCC in ITU-T) and the call controller at the network side of ASON (called NCC in ITU-T standards).
As shown in FIG. 1, there are four interconnected ASON domains (Domain 1˜4), the network elements on the boundary of the domains are responsible for the call, i.e. implementing NCC. All network elements in the domain (including those on boundary) are responsible for connection establishment, i.e. implementing CC. For brief description, CC responsible for the connection processing will be illustrated according to the need of description in the following demonstration.
Following the gradual commercialization of ASON in recent years, the need for interconnection of different ASONs is more and more urgent. However, ITU-T and other standard organizations have not developed relative interconnection standard to complete the cross-domain call and connection establishment. As shown by the dashed line in the accompanying FIG. 1, there is no relative standards and techniques to solve the problem of how to implement the call and connection between the user equipment to which CCC1a belongs and the user equipment to which CCC4b belongs via their own respective ASON domain.